TWO ROUNDS: WBC middleweight champion Julio Cesar Chavez Jr. (left) and Sergio Martinez are one of two major fights taking place tonight in Las Vegas on HBO pay-per-view and Showtime. Photo: Reuters

TWO ROUNDS: WBC middleweight champion Julio Cesar Chavez Jr. (left) and Sergio Martinez are one of two major fights taking place tonight in Las Vegas on HBO pay-per-view and Showtime. (
)

It’s the best of boxing and the worst of boxing on a night that either could cultivate more boxing fans or turn them off.

No, it doesn’t make a lot of sense to have two major boxing cards on the same night at different venues in the same city. But that’s what happening tonight in Las Vegas.

At the Thomas and Mack Center at UNLV, Sergio Martinez and Julio Cesar Chavez Jr. will headline an HBO pay-per-view card when they meet for Chavez’s WBC middleweight championship.

At roughly the same time, Canelo Alvarez will defend his WBC super welterweight title against Josesito Lopez at the MGM Grand. Their bout will be televised on Showtime.

Having competing fight cards on the same night in different cities is nothing new in boxing, though the powers at HBO and Showtime swear they do their best to avoid such conflicts. But tonight’s Vegas boxing buffet is more of a standoff in the ongoing feud between promoters Top Rank Inc. and Oscar De La Hoya’s Golden Boy Promotions.

Top Rank is promoting the Martinez-Chavez card and Golden Boy Promotions is behind Alvarez-Lopez. Golden Boy initially planned to have Alvarez fight Paul Williams on HBO, but Williams was paralyzed in a motorcycle accident in May. While Alvarez looked for another opponent, Martinez and Chavez agreed to fight and HBO deemed that worthy of pay-per-view complete with a 24/7 series.

With Mexican Independence Day being celebrated this weekend, neither promotional company wanted to move their date. So now we have boxing overload. Maybe it’s a bad thing. Maybe it’s a good thing.

Chavez-Martinez is one of the most anticipated bouts of the year. The son of Mexican boxing legend Julio Cesar Chavez was noticed more for his name than his talent early in his career. But he developed to the point where he won the WBC belt last year and has successfully defended it three times.

But Chavez Jr. (46-0-1, 32 KOs) will not be recognized as the true champion until he defeats Martinez (49-2-2, 28 KOs). The Argentinian won the same belt in 2010 by beating Kelly Pavlik, but was stripped of the title despite stopping his last four opponents, who entered the ring with a combined record of 127-4.

“I cannot accept the fact he is world champion,” the 37-year-old Martinez said. “The only reason he is world champion is because he is Julio Cesar Chavez Jr., the son of the legend. But he has a big mouth and he’s talking too much.”

Chavez Jr., 26, relishes the chance to validate his title.

“I’m about fighting the best fighters,” he said. “I am very confident I am going to win the fight and that I will give everyone a fight that they will remember for a long time.”

Lopez (30-4, 18 KOs) got the chance to face Alvarez (40-0-1, 29 KOs) by upsetting Victor Ortiz, who was in line to meet Alvarez, the popular 22-year-old redhead from Mexico. Lopez, who lives in Riverside, Calif., was a junior welterweight before moving up to welterweight to fight Ortiz last June. Now he’s making another leap to challenge for the 154-pound title.

“I understand that I have to fight the best fight of my life to come out with a victory, and for that reason I prepared really well,” Lopez, 28, said. “It’s going to be important to get Canelo’s attention early and be smart in the early rounds. Size means nothing to me — I was always the smaller kid fighting the bigger guys.”

Alvarez is heavily favored but said he won’t overlook Lopez.

“I grew up dreaming about what it would be like to fight on a stage like this and now I am here,” he said. “I want to take advantage of this fight, this opportunity and stay here for a long time. We had plenty of time to get prepared for this fight. I am not underestimating Josesito Lopez one bit.”